1. Field of the Invention
The present invention concerns a proximity detector of the inductive, photoelectric or any other type, comprising a sensor unit adapted to deliver an analogue detection signal according to the range of a target and an electronic processor circuit connected to an output stage that delivers a signal indicating the presence or the absence of a target according to whether the range of the target is less than or greater than a switching distance.
2. Discussion of the Background
The switching distance specific to a detector of this kind varies from one equipment to another and, for the same equipment, with its installation or environmental conditions, in particular in the case of an inductive detector embedded in a mass of metal or a photoelectric cell operating with a bright background.
It would therefore be useful to be able to calibrate the proximity detector in situ.
It has previously been proposed (see document DE-43 31 555) to calibrate a proximity detector in the factory or on the user's premises using control logic to which a non-volatile memory and a counter are connected. An object is placed at a predetermined fixed distance from the detector and counting is started when the logic is activated by a calibration signal; the count value is passed through a digital-to-analogue converter and then compared with the value of the detected signal; as soon as it reaches this value, the count is stopped and the corresponding value is placed in memory. However, a device of this kind cannot be used with a target that moves during the calibration phase.